Home > Welded Tubes > Duplex & Super Duplex Welded Tubes
INOX STEEL INDIA is one of India’s most trusted suppliers of Duplex (S31803/S32205) and Super Duplex (S32750/S32760) Welded Tubes, engineered for environments where chlorides, pressure, temperature and corrosive chemicals can destroy standard stainless steel.
Designed for offshore structures, desalination plants, refineries, chemical reactors, seawater systems and high-pressure heat exchangers, our Duplex & Super Duplex welded tubes offer superior strength, outstanding chloride resistance and long-term stability. All tubes are manufactured, welded, solution annealed, pickled, tested and certified as per ASTM A789 / ASTM A790.
Duplex stainless steels are 50% ferrite + 50% austenite, giving them:
Super Duplex grades (S32750 / S32760) offer even higher chromium, molybdenum and nitrogen levels — delivering PREN > 40–45, ideal for the most severe corrosive conditions.
These welded tubes undergo:
✔ TIG / Plasma / Laser welding | ✔ Bead control | ✔ Full solution annealing | ✔ Pickling & passivation | ✔ 100% PMI | ✔ NDT (EC/UT/PT/RT)
Ensuring corrosion stability and weld soundness.
Duplex 2205 (S31803 / S32205)Best for: High-pressure heat exchangers, Chemical plants, Lean seawater applications.
Super Duplex 2507 (S32750 / S32760)Best for: Offshore platforms, Subsea piping, High-chloride & seawater systems, Desalination plants.
(For seamless & welded duplex/super-duplex tubing applications — weld-focused where required)
| Section | Parameter | Technical Specification (Duplex & Super Duplex Welded Tubes) |
|---|---|---|
| General | Product | Duplex & Super Duplex Stainless Steel Welded Tubes |
| Grades | Duplex: S31803, S32205 (2205) • Super Duplex: S32750, S32760 (2507) | |
| UNS Numbers | Duplex: S31803 / S32205 • Super Duplex: S32750 / S32760 | |
| Standards | ASTM A789 (Duplex Tubing) • ASTM A790 (Duplex & Super Duplex Pipe/Tubes) | |
| Product Form | Welded tubes (TIG / GTAW welded, solution annealed & pickled) | |
| Chemical Composition (Typical %) | Duplex S31803/S32205 | Cr 21–23%, Ni 4.5–6.5%, Mo 2.5–3.5%, N 0.08–0.20%, Fe balance |
| Super Duplex S32750 | Cr 24–26%, Ni 6–8%, Mo 3–5%, W ≤1%, N 0.24–0.32%, Fe balance | |
| Super Duplex S32760 | Cr 24–26%, Ni 6–8%, Mo 3–4%, Cu ≤0.5%, W ~0.5–1%, N ~0.20–0.30%, Fe balance | |
| Mechanical Properties | Duplex (S32205) | YS ≥ 450 MPa • TS ≥ 620 MPa • Elongation ≥ 25% |
| Super Duplex (S32750/S32760) | YS ≥ 550 MPa • TS ≥ 795 MPa • Elongation ≥ 25% | |
| Corrosion Resistance | Key Feature | High resistance to pitting, crevice, stress corrosion cracking (SCC), seawater chlorides |
| PREN Values | Duplex ~35–38 • Super Duplex >40–45 (excellent chloride resistance) | |
| Temperature Range | Recommended | –50°C to +300°C (above 300°C duplex phases become unstable) |
| Welding Characteristics | Weld Method | TIG / Plasma / Laser welding |
| Heat Treatment | Mandatory solution annealing after welding to restore duplex phase balance | |
| Filler Wire | Duplex: ER2209 • Super Duplex: ER2594, ER2553 | |
| Weld Requirements | Ferrite content 30–70% (ASTM A923 test optional) | |
| Dimensional Range | OD Range | 6 mm – 254 mm |
| Wall Thickness | 1.0 mm – 12.7 mm | |
| Lengths | 6m standard, 12m optional, custom cut | |
| Shapes | Round (standard), limited square/rectangular | |
| Testing Requirements | Mandatory NDT | Eddy Current / Hydrotest / Visual & Dimensional |
| Optional | ASTM A923 (Duplex toughness test) • PT, UT, RT | |
| Additional | PMI, Flattening, Flaring, Hardness | |
| Surface Finish | Standard | Pickled & Passivated |
| Optional | Bright Annealed, Polished OD | |
| End Conditions | End Type | Plain Ends (PE), bevelled ends on request |
| Advantages | Duplex | 2x strength of SS 316L, better chloride resistance |
| Super Duplex | Exceptional seawater resistance, high mechanical strength | |
| Applications | Offshore Oil & Gas | Subsea piping, umbilicals, flowlines |
| Marine | Seawater cooling tubes | |
| Chemical Process | Reactors, heat exchangers | |
| Desalination | Evaporators, RO systems | |
| Pulp & Paper | Chloride-rich bleaching | |
| Power & Energy | Heat exchanger and boiler tubes | |
| HSN Codes | Duplex / Super Duplex Tubes | 7304 / 7306 (for SEO ref.) |
1. Offshore & Marine
2. Desalination & Water Treatment
3. Oil & Gas
4. Chemical & Petrochemical
5. Power & Energy
6. Pulp & Paper
| Parameter | Duplex 2205 | Super Duplex 2507 |
|---|---|---|
| PREN | ~35–38 | >40–45 |
| Strength | High | Very High |
| SCC Resistance | High | Excellent |
| Seawater Corrosion | Good | Excellent |
| Cost | Moderate | Higher |
| Application | Chemical, moderate chloride | Offshore, high chloride, extreme corrosion |
| Outside Diameter (OD) | Wall Thickness (WT) | Applications |
|---|---|---|
| 6 – 12.7 mm | 1.0 – 1.6 mm | Control lines, instrumentation |
| 12.7 – 25.4 mm | 1.0 – 2.0 mm | Chemical injection lines |
| 25.4 – 50.8 mm | 1.5 – 4.0 mm | Heat exchangers |
| 50.8 – 114 mm | 2.0 – 6.0 mm | Process piping, brine systems |
| 114 – 168 mm | 2.0 – 10 mm | Desalination, offshore piping |
| 168 – 254 mm | 3.0 – 12.7 mm | Heavy-duty seawater systems |
Lengths: 6m standard • 12m optional • Custom cut lengths available.
| Grade | PREN Value | Chloride Resistance | Typical Service |
|---|---|---|---|
| S31803 | 35–38 | High | Chemical, offshore support |
| S32205 | 35–40 | Very High | High-pressure heat exchangers |
| S32750 (2507) | 40–45 | Excellent | Desalination, offshore, subsea |
| S32760 | 42–47 | Exceptional | Oil & gas, chlorine-rich systems |
Key Insight: Higher PREN = better resistance to chloride-induced corrosion, critical for seawater & brine applications.
Welding Methods Used in Manufacturing: TIG / GTAW, Plasma Welding, Laser Welding, Automatic Orbital Welding for small OD.
Ideal Filler Wires for Duplex & Super Duplex:
| Base Material | Filler Wire | Code | Notes |
|---|---|---|---|
| S31803 / S32205 | ER2209 | AWS A5.9 | Ensures correct ferrite-austenite balance |
| S32750 / S32760 | ER2594 | AWS A5.9 | Matches super duplex alloy chemistry |
| Super Duplex (alternate) | ER2553 | — | Higher alloying for chloride resistance |
Critical Post-Weld Steps: ✔ Solution annealing at ~1020–1120°C | ✔ Rapid quenching to avoid sigma phase formation | ✔ Ferrite number verification (30–70%) | ✔ Pickling & passivation.
| Operating Condition | Recommended Grade | Reason |
|---|---|---|
| Moderate chlorides (brackish water) | S31803 / S32205 | Balanced corrosion + strength |
| High chlorides (seawater) | S32750 | High PREN value |
| Extreme chlorides + high pressure | S32760 | Maximum pitting resistance |
| High-pressure heat exchangers | S32205 | Excellent fatigue + SCC resistance |
| Subsea oil & gas | S32760 | Toughness + corrosion resistance |
Mandatory Tests (As per ASTM A789 / A790)
✔ Hydrostatic Test
✔ 100% PMI Testing
✔ Eddy Current Test
✔ Visual & Dimensional Inspection
✔ Flattening / Flaring Tests
✔ Tensile / Hardness
Advanced Optional Tests
✔ ASTM A923 — Detects deleterious phases in duplex
✔ Ferrite Number Check (FN 30–70)
✔ Dye Penetrant (PT)
✔ Ultrasonic Testing (UT)
✔ Radiography (RT) on weld
✔ Corrosion tests (ASTM G48 for chloride pitting)
Inspection Documents
We provide:
| Grade | Type | INR Price/Kg | USD Price/Kg |
|---|---|---|---|
| Duplex S31803/S32205 | Welded Tube | ₹ 650 – ₹ 1,100 | $8 – $14 |
| Super Duplex S32750 | Welded Tube | ₹ 1,100 – ₹ 1,850 | $14 – $23 |
| Super Duplex S32760 | Welded Tube | ₹ 1,250 – ₹ 2,200 | $15 – $27 |
| Finish | Applications |
|---|---|
| Pickled & Passivated | Process piping, chemical units |
| Bright Annealed | Heat exchangers, food-grade |
| Polished | Architectural, marine |
| Cleaned & Degreased | Offshore, subsea, oxygen-rich systems |
Oil & Gas / Offshore / Subsea
Desalination / Marine
Chemical / Petrochemical
Power & Paper Industries
Duplex & Super Duplex tubes are used in the most demanding environments. INOX STEEL INDIA is trusted worldwide because:
Stock Locations: Mumbai • Pune • Ahmedabad • Vadodara • Chennai • Hyderabad • Delhi NCR • Bengaluru.
Compliance: We export globally with 100% compliance including 3.1 docs, NACE + MTC, PMI, and A923 test results.
| Industry | Why Duplex/Super Duplex is Used | Recommended Grade |
|---|---|---|
| Offshore / Subsea | Seawater + chloride stress | S32750 / S32760 |
| Desalination (RO/Brine) | Chloride-rich brine | S32750 |
| Oil & Gas (Upstream/Downstream) | Sour service + pressure | S32205 / S32760 |
| Chemical Processing | Mixed acids, chlorides | S31803 / S32205 |
| Marine | Corrosion & erosion | S32750 |
| Pulp & Paper | Bleach plants, chlorine dioxide | S31803 |
| Power & Energy | Heat exchangers | S32205 |
✔ STANDARD PACKAGING
✔ EXPORT PACKAGING
✔ DOCUMENTATION
For Duplex 2205 (S31803/S32205) and Super Duplex 2507 (S32750/S32760) welded tubes
52-A, Mulji Thackersi Bldg, Islampura Street, Shop No. 10, Near Alankar Cinema, Mumbai – 400 004
steel@inoxsteelindia.in
+91 9930796690
Pitting Resistance Equivalent Number:
Higher PREN = better seawater resistance.
Yes — solution annealing is mandatory to maintain phase balance.
ASTM A789 / A790 for duplex & super duplex tubes.
Yes — fully certified with PMI, NDT & solution annealing charts.
Manufacturer and supplier of Duplex & Super Duplex Welded Tubes in grades S31803, S32205, S32750, S32760 (2205 & 2507). TIG/Laser welded, solution annealed & NDT-tested as per ASTM A789/A790. Used in offshore, desalination, chemical, petrochemical & seawater systems. Exporter to Europe, USA & Middle East.